This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

You don't tell us what troubleshooting you've already done. Assuming you've verified that this is originating on your server, verify that your mail server is not acting as an open relay. If you're sure that's not the problem proceed through your server's logs to determine if the system was compromised, and and if it is compromised proceed per the linked duplicate question. If you have specific questions on any of these aspects feel free to ask a new question...
–
voretaq7♦Jan 7 '13 at 17:41

Since you've chosen to munge a lot of the relevant information, it's very hard to help you with this particular mail. It'd be a lot easier if you'd kept the original hostnames and ip addresses. It's entirely possible that this email wasn't even sent through your system, but since you're hiding all that information, I can't tell.